1. Field of the Invention
Systems for analyzing human speech, for determining the pitch of speech segments operate in many different ways. To obtain more accurate results, some use more than one pitch detection algorithm.
2. Description of the Prior Art
A system as defined above is known from Prior Art References. In the system described therein, use is made of the autocorrelation method, the spectrum method and of the low-pass filter wave form method. As described in this publication the choice of these methods is determined by the wish to obtain reasonably independent estimates of the pitch.
The autocorrelation method directly uses Prior Art information from the time domain, whereas the spectrum method utilizes information from the frequency domain. Other methods using information from the frequency domain are known, for example the Prior Art harmonic sieving method. Therein, the amplitude spectrum is determined for a short segment (40 ms) of the sampled signal and thereafter a search is made in the amplitude spectrum for the frequency positions of the significant peaks of the amplitude (significant peak positions) and finally--by what is denoted as the harmonic sieve--a pitch is sought for, whose harmonics are the closest match to the significant peak positions of the amplitude spectrum.
In the methods mentioned here for determining the pitch in speech, problems arise which are characteristic of each method. In general it can be said that methods operating in the frequency domain frequently make errors when used for high pitches and that methods operating in the same domain make errors for lower pitches and often indicate multiples of the actual pitch as the pitch.